Synthesis and characterization of monoaryl esters of l-tartaric acid and their process for fries rearrangement

Article abstract of DOI:10.1007/s13738-015-0657-1

Chiral protected monoaryl esters (2a-2h) were synthesized from monoester of l-tartaric acid, having two asymmetric centers and C2 axis of symmetry. l-tartaric acid was protected and partially hydrolyzed to give the corresponding monoester. Monoester upon treatment with different substituted phenols gave desired monoaryl esters (2a-2h). Fries rearrangement of monoaryl esters was then tried under various conditions by using different Lewis acids. All the compounds were purified and characterized by using spectroscopic techniques like IR, ¹H-NMR, ¹³C-NMR, HRMS-ESI, and elemental analysis. The structure of compound 2e was obtained by X-ray crystallography.

Full text of DOI:10.1007/s13738-015-0657-1

J IRAN CHEM SOC
DOI 10.1007/s13738-015-0657-1
ORIGINAL PAPER
Synthesis and characterization of monoaryl esters of l‑tartaric
acid and their process for fries rearrangement
Sher Wali Khan1,2 · Javaid Hussain Zaidi · Gul Shahzada Khan ·
2
1
3
4
1
Haroon Ur Rashid · Muhammad Naveed Umar · Abdul Khaliq Jan ·
5
5
Carman Galan · Mairi Haddow
Received: 26 August 2014 / Accepted: 30 April 2015
Iranian Chemical Society 2015
©
Abstract Chiral protected monoaryl esters (2a–2h) were
synthesized from monoester of l-tartaric acid, having two
asymmetric centers and C2 axis of symmetry. l-tartaric
acid was protected and partially hydrolyzed to give the
corresponding monoester. Monoester upon treatment with
different substituted phenols gave desired monoaryl esters
derivatives of tartaric acid have wide applications in the
synthesis of numerous chiral building blocks [1–3]. In addi-
tion, it is also used as a precursor of chiral ligands, auxilia-
ries, and resolving agents [4–8]. Among the derivatives of
tartaric acid, its dialkyl esters are most frequently used, not
only for the preparation of other tartaric acid derivatives but
also in asymmetric catalysis, for example, as chiral ligands
in the Sharpless asymmetric epoxidation [9, 10], kinetic
resolution of racemic allyl alcohols [11, 12], asymmet-
ric synthesis of sulfoxides by the Kagan-Modena method
[13–16], asymmetric Simmons-Smith reaction [17–20],
asymmetric allylation [21–23], asymmetric allylboration
developed by Roush [24, 25], and homoallenylboration of
aldehydes developed by Brown [26].
(2a–2h). Fries rearrangement of monoaryl esters was then
tried under various conditions by using different Lewis
acids. All the compounds were purified and characterized
1
13
by using spectroscopic techniques like IR, H-NMR, C-
NMR, HRMS-ESI, and elemental analysis. The structure of
compound 2e was obtained by X-ray crystallography.
Keywords l-Tartaric acid · Protection · Monoaryl esters ·
Fries rearrangement
Keeping in view the importance of l-tartaric acid deriva-
tives, we planned to synthesize some new chiral substrates
of potential value for synthetic and biological applications.
Introduction
Tartaric acid is an important optically active compound. It
has been used to study the stereochemistry. The different
Experimental
Materials and methods
*
Sher Wali Khan
sherwalikhn@yahoo.co.uk
All chemicals were of highest purity available and used
as supplied. Dry solvents like methanol, dichlorometh-
ane, chloroform, and n-hexane were obtained by distil-
lation using standard procedures or by passage through
a column of anhydrous alumina using equipment from
anhydrous engineering (University of Bristol, UK) based
on the Grubbs’ design. Reactions were carried out under
anhydrous conditions using three-way stopcock and rubber
septa.
1
2
3
4
5
Department of Chemistry, Shaheed BB University Sheringal,
Dir (Upper), KPK, Pakistan
Department of Chemistry, Quaid-I-Azam University,
Islamabad, Pakistan
Department of Chemistry, Sarhad University of Science
and Information Technology, Peshawar, KPK, Pakistan
Department of Chemistry, University of Malakand,
Chakdara, KPK, Pakistan
All reactions were monitored by TLC on Kieselgel 60
F254 (Merck), and ethyl acetate/n-Hexane and methanol/
chloroform were used as eluents.
School of Chemistry University of Bristol, Bristol, United
Kingdom
1
3

J IRAN CHEM SOC
Column chromatography was performed using silica gel
The aqueous layer was acidified with KHSO (1 M) and
4
[
Merck, 230–400 mesh (40–63 μm)]. Melting points were
extracted with DCM (30 ml × 3). The solvent was evapo-
rated and the crude was purified by column chromatogra-
phy using methanol:dichloromethane (2:8) as eluent.
determined in degree Celsius (°C) using Gallenkamp digi-
tal melting point apparatus and are uncorrected. IR spectra
were recorded on Bruker IFS 66 (FT IR), Nicolet 205 FT
IR; Nicolet 360 smart orbit (ATR); thermo scientific Nico-
let 6700 FT IR and Schimadzu Fourier Transform Infra-
red Spectrophotometer Model 270. H NMR spectra were
recorded on NMR Bruker apparatus at 300 MHz and var-
ian 400 MHz INOVA instrument. C NMR spectra were
recorded on NMR Bruker apparatus at 75 MHz and varian
−1
Colorless oil. Yield: 79 %. IR (neat) cm : 3467 (OH),
1
2928 (CH), 1730 (COOCH ), 1708 (COOH). H NMR
3
(300 MHz, CDCl ): δ (ppm): 9.31 (bs, 1H, OH), 4.87 (d,
3
1
J = 5.4 Hz, 1H, CH), 4.82 (d, J = 5.4 Hz, 1H, CH), 3.82
1
3
(s, 3H, OCH ), 1.49 (s, 3H, CH ), 1.47 (s, 3H, CH ).
C
3
3
3
1
3
NMR (75 MHz, CDCl ): δ (ppm): 173.8 (COOH), 169.7
3
(COOCH ), 114.1 (qt C), 76.5 (CH), 76.3 (CH), 52.8
3
1
00 MHz INOVA instrument. The optical rotations of the
(OCH ), 26.1 (CH ), 25.5 (CH ). HRMS-ESI for C H O :
3
3
3
8
12
6
compounds were measured on ATAGO, AP-100 automatic
polarimeter. Single-crystal X-ray diffraction data were col-
lected on Bruker Smart APEX II, CCD 4-K area detector
diffractometer [27]. Data reductions were performed by
using SAINT program. The structure was solved by direct
method [28] and refined by full-matrix least squares on F2
by using the SHELXTL-PC package [29]. The figures were
plotted with the aid of ORTEP program [30].
(M-H) calcd: 203.0634, found: 203.0570. EI-MS m/z (%):
204.0 M (10.6), 189.1 (35.9), 59.0 (100).
+
General procedure for the synthesis of monoaryl esters
(2a–2h)
In a round bottom flask (100 ml), compound (2) (0.61 g,
3 mmol) in DCM (30 ml), 1-ethyl-3-(3-dimethylamino-
propyl) carbodiimide (EDC) (0.68 g, 3.6 mmol), and cata-
lytic amount of 4-dimethylaminopyridine (DMAP) were
placed under nitrogen. After half an hour substituted phe-
nol (3 mmol) was added and stirred for 4–12 h. After the
completion of the reaction, by-product urea was removed
by extraction with ethyl acetate or chloroform and water
(30 × 3). Crude was purified by column chromatography
using ethyl acetate: n-hexane (3:7) as eluent.
General procedure for the synthesis of 1,3‑dioxolane
dimethyl‑l‑tartrate (1)
In a round bottom flask (250 ml), dimethyl-l-tartrate (35.60 g,
2
00 mmol) and catalytic amount of camphor sulfonic acid
were placed under nitrogen. Dimethylformamide (DMF)
100 ml) was added through a syringe and stirred with a mag-
(
netic stirrer. 2-Methoxypropene (22.90 ml, 240 mmol,) was
added drop wise over 1 h and left overnight. After comple-
tion of the reaction as monitored by TLC, water (300 ml) was
added to the reaction mixture and extracted with ethyl acetate
(4R,5R)‑4‑Methyl‑5‑phenyl‑2,2‑dimethyl‑1,3‑diox‑
olane‑4,5‑dicarboxylate (2a)
2
5
(
100 ml × 3). The organic layer was washed with saturated
Yield: 78 %. Colorless oil. [α] = 72.58° (c = 24 mg/2 ml
D
−
CH Cl ). (IR υ cm ): 2992 (CH), 1756 (COOPh), 1732
2 2
1
NaHCO (100 ml × 2), water, and brine (100 × 3). The com-
3
1
bined organic layer was dried over anhydrous magnesium
sulfate; the crude was purified by column chromatography
using ethyl acetate: n-hexane (2:8) as eluent.
(COOCH ) 1592 (Ar), 1324 (C–O–C). H NMR (400 MHz,
3
CDCl ): δ (ppm): 7.44–7.14 (m, 5H, Ar–H), 5.06 (d, 1H,
3
J = 5.3 Hz, CH), 4.99 (d, 1H, J = 5.3 Hz, CH), 3.87 (s,
−
1
13
Light yellow oil. Yield: 89 %. IR (neat) cm : 2928
3H, O-CH ), 1.58 (s, 3H, CH ), 1.51 (s, 3H, CH ).
C
3
3
3
1
(
CH), 1738 (CO). H NMR (300 MHz, CDCl ): δ (ppm):
NMR (100 MHz, CDCl ): δ (ppm): 170.7 (COOPh), 168.5
3
3
4
.78 (s, 2H, CH), 3.80 (s, 6H, OCH ) 1.47 (s, 6H, CH ).
(COOCH ), 150.8 (Ar–C–OR), 129.6, 126.5, 121.8 (Ar–C),
3
3
3
1
3
C NMR (75 MHz, CDCl ): δ (ppm): 170.0 (CO), 113.8
114.7 (qt, C), 76.5 (CH), 75.2 (CH), 53.4 (OCH ), 26.3 (CH ),
3
3
3
+
(qt C), 76.6 (CH), 52.7 (OCH ), 26.2 (CH ).
25.1 (CH ). HRMS-ESI for C H O Na: [M+Na] calcd:
3
3
3
14 16 6
3
03.0945, found: 303.0845. Anal. Calc. For C H O : C,
14 16 6
General procedure for the synthesis of monoester (2)
59.99; H, 5.75; O, 34.25. Found C, 59.96; H, 5.77; O, 34.27.
In a round bottom flask (250 ml), a solution of compound 1
(4R,5R)‑4‑Methyl‑5‑p‑tolyl‑2,2‑dimethyl‑1,3‑diox‑
(22.74 ml, 120 mmol) in methanol (30 ml) was added to a
olane‑4,5‑dicarboxylate (2b)
solution of NaOH (4.80 g, 120 mmol) in methanol (30 ml)
over a period of 1 h. The reaction mixture was stirred at
room temperature for an additional 1 h and methanol was
evaporated under reduced pressure to give a residue. Water
2
D
5
Yield: 83 %. Yellow Oil. [α] = 70.51° (c = 24 mg/2 ml
−1
CH Cl ). (IR υ cm ): 2994 (CH), 1751 (COOPh),
1730 (COOCH ), 1590 (Ar), 1321 (C–O–C). H NMR
2
2
1
3
(
30 ml) was added and extracted with Dichloromethane
(400 MHz, CDCl ): δ (ppm): 7.54 (d, J = 8.3 Hz, 2H,
3
(DCM) (30 ml × 3) to recover some unreacted diester.
Ar–H), 6.99 (d, J = 8.4 Hz, 2H Ar–H), 5.03 (d, 1H,
1
3

J IRAN CHEM SOC
J = 5.3 Hz, CH), 4.96 (d, 1H, J = 5.3 Hz, CH), 3.85 (s,
(ppm): 7.35 (s, 1H, Ar–H), 6.99 (d, J = 8.4 Hz, 2H Ar–H),
5.02 (d, 1H, J = 5.0 Hz, CH), 4.94 (d, 1H, J = 5.0 Hz,
CH), 3.86 (s, 3H, OCH ), 2.39 (s, 3H, Ar–CH ), 1.55 (s,
3
H, O-CH ), 2.35 (s, 3H, Ar–CH ), 1.56 (s, 3H, CH ), 1.46
3 3 3
1
3
(
s, 3H, CH3). C NMR (100 MHz, CDCl ): δ (ppm): 170.3
3
3
3
1
3
(
COOPh), 169.4 (COOCH ), 147.5 (Ar–C–OR), 136.4,
3H, CH ), 1.45 (s, 3H, CH ). C NMR (100 MHz, CDCl3):
3 3
3
1
5
30.5, 120.9 (Ar–C), 113.7 (qt, C), 75.3 (CH), 74.3 (CH),
2.5 (O–CH ), 26.6 (CH ), 25.6 (CH ), 20.4 (Ar–CH ).
δ (ppm): 169.9 (COOPh), 168.3 (COOCH ), 148.5 (Ar–C–
3
OR), 136.7, 131.8, 125.5, 124.3, 120.3 (Ar–C), 114.8 (qt,
C), 76.1 (CH), 75.3 (CH), 53.6 (OCH ), 26.7 (CH ), 25.5
3
3
3
3
+
HRMS-ESI for C H O Na: [M+Na] calcd: 317.1001,
1
5
18
6
3
3
found: 317.0984. Anal. Calc. For C H O : C, 61.22; H,
(CH ), 22.3 (Ar–CH ). HRMS-ESI for C H BrO Na:
3 3 15 17 6
1
5
18
6
+
6
.16; O, 32.62 Found C, 61.25; H, 6.13; O, 32.66.
[M+Na] calcd: 395.0106, found: 395.0209. Anal. Calc.
For C H BrO : C, 48.28; H, 4.59; Br, 21.41; O, 25.72
1
5
17
6
(4R,5R)‑4‑(3‑Bromophenyl)‑5‑methyl‑2,2‑dime‑
Found C, 48.30; H, 4.57; Br, 21.44; O, 25.70.
thyl‑1,3‑dioxolane‑4,5‑dicarboxylate (2c)
(
4R,5R)‑4‑Methyl‑5‑m‑tolyl‑2,2‑dimethyl‑1,3‑diox‑
2
D
5
Yield: 85 %. Yellow Oil. [α] = 54.17° (c = 24 mg/2 ml
olane‑4,5‑dicarboxylate (2f)
−1
CH Cl ). (IR υ cm ): 2984 (CH), 1751 (COOPh), 1722
COOCH ), 1594 (Ar), 1311 (C–O–C), 563 (C–Br). H NMR
400 MHz, CDCl ): δ (ppm): 7.39 (s, 1H, Ar–H), 7.36–7.30
2
2
1
25
D
(
(
(
Yield: 80 %. Brown Oil. [α] = 74.51° (c = 24 mg/2 ml
3
−
CH Cl ). (IR υ cm ): 2983 (CH), 1753 (COOPh),
2 2
1
3
1
m, 3H, Ar–H) 5.00 (d, 1H, J = 5.5 Hz, CH), 4.92 (d, 1H,
1733 (COOCH ), 1581 (Ar), 1321 (C–O–C). H NMR
(400 MHz, CDCl ): δ (ppm): 7.38 (s, 1H, Ar–H), 7.05–
3
J = 5.5 Hz, CH) 3.83 (s, 3H, O-CH ), 1.55 (s, 3H, CH ),
3
3
3
13
1
1
1
7
.51 (s, 3H, CH ). C NMR (100 MHz, CDCl ): δ (ppm):
6.99 (m, 3H Ar–H), 5.03 (d, 1H, J = 5.3 Hz, CH), 4.96
3
3
70.5 (COOPh), 169.8 (COOCH ), 150.5 (Ar–C–OR),
30.4, 129.6, 124.7, 122.5 (Ar–C), 114.1 (qt, C), 76.3 (CH),
5.6 (CH), 53.4 (OCH ), 26.8 (CH ), 25.4 (CH ). HRMS-
(d, 1H, J = 5.3 Hz, CH), 3.85 (s, 3H, OCH ), 2.36 (s,
3
3
1
3
3H, Ar–CH ), 1.56 (s, 3H, CH ), 1.46 (s, 3H, CH ).
C
3
3
3
NMR (100 MHz, CDCl ): δ (ppm): 169.7 (COOPh), 168.6
(COOCH ), 150.7 (Ar–C–OR), 139.7, 129.6, 127.6, 121.0,
118.2 (Ar–C), 114.6 (qt, C), 76.3 (CH), 75.5 (CH), 53.5
(OCH ), 26.7 (CH ), 25.7 (CH ), 21.8 (Ar–CH ). HRMS-
3
3
3
3
+
ESI for C H BrO Na: [M+Na] calcd: 380.9950, found:
14
15
6
3
3
80.9948. Anal. Calc. For C H BrO : C, 48.28; H, 4.59; Br,
14
15
6
2
1.41; O, 25.72 Found C, 48.30; H, 4.56; Br, 21.44; O, 25.70.
3
3
3
3
+
ESI for C H O Na: [M+Na] calcd: 317.1001, found:
1
5
18
6
(
4R,5R)‑4‑(3‑Chloro‑4‑methylphenyl)‑5‑methyl‑2,2‑di‑
317.0984. Anal. Calc. For C H O : C, 61.22; H, 6.16; O,
15 18 6
methyl‑1,3‑dioxolane‑4,5‑dicarboxylate (2d)
32.62 Found C, 61.25; H, 6.18; O, 32.60.
2
D
5
Yield: 87 %. Yellow oil. [α] = 60.35° (c = 24 mg/2 ml
(4R,5R)‑4‑(2‑Bromophenyl)‑5‑methyl‑2,2‑dime‑
thyl‑1,3‑dioxolane‑4,5‑dicarboxylate (2g)
−
1
CH Cl ). (IR υ cm ): 2983 (CH), 1747 (COOPh), 1723
COOCH ) 1581 (Ar), 1316 (C–O–C), 736 (C–Cl). H
NMR (400 MHz, CDCl ): δ (ppm): 7.63 (s, 1H, Ar–H),
2
2
1
(
3
2
5
Yield: 74 %. Brown Oil. [α] = 49.15° (c = 24 mg/2 ml
3
D
−
CH Cl ). (IR υ cm ): 2973 (CH), 1749 (COOPh), 1727
2 2
1
6
.95 (d, J = 8.4 Hz, 2H, Ar–H), 5.01 (d, 1H, J = 4.9 Hz,
1
CH), 4.94 (d, 1H, J = 4.9 Hz, CH), 3.85 (s, 3H, OCH ),
(COOCH ), 1591 (Ar), 1311 (C–O–C), 567 (C–Br). H NMR
3
3
2
.35 (s, 3H, Ar–CH ), 1.56 (s, 3H, CH ), 1.46 (s, 3H, CH ).
(400 MHz, CDCl ): δ (ppm): 7.63–7.14 (m, 4H, Ar–H), 5.15
3
3
3
3
1
3
C NMR (100 MHz, CDCl ): δ (ppm): 169.6 (COOPh),
(d, 1H, J = 5.4 Hz, CH), 5.11 (d, 1H, J = 5.4 Hz, CH), 3.86
3
13
1
68.2 (COOCH ), 148.5 (Ar–C–OR), 134.4, 134.1, 131.3,
(s, 3H, O–CH ), 1.55 (s, 3H, CH ), 1.45 (s, 3H, CH ).
C
3
3
3
3
1
21.5, 119.7 (Ar–C), 114.6 (qt, C), 75.5 (CH), 74.3
NMR (100 MHz, CDCl ): δ (ppm): 169.9 (COOPh), 167.8
3
(
CH), 53.5 (O–CH ), 26.8 (CH ), 25.8 (CH ), 19.7 (Ar-
(COOCH ), 147.9 (Ar–C–OR), 133.8, 128.7, 127.5, 123.6
3
3
3
3
+
CH ). HRMS-ESI for C H ClO Na: [M+Na] calcd:
(Ar–C), 114.6 (qt, C), 76.1 (CH), 75.3 (CH), 52.7 (OCH3),
26.3 (CH ), 25.7 (CH ). HRMS-ESI for C H BrO Na:
3
15 17
6
3
51.0611, found: 351.0602. Anal. Calc. For C H ClO :
15 17 6
3
3
14 15
6
+
C, 54.80; H, 5.21; Cl, 10.78; O, 29.20 Found C, 54.83; H,
.24; Cl, 10.75; O, 29.17.
[M+Na] calcd: 380.9950, found: 380.9946. Anal. Calc. For
5
C H BrO : C, 48.28; H, 4.59; Br, 21.41; O, 25.72 Found
14
15
6
C, 48.31; H, 4.53; Br, 21.40; O, 25.70.
(4R,5R)‑4‑(3‑Bromo‑4‑methylphenyl)‑5‑methyl‑2,2‑di‑
methyl‑1,3‑dioxolane‑4,5‑dicarboxylate (2e)
(4R,5R)‑4‑(2,4‑Dichlorophenyl)‑5‑methyl‑2,2‑dime‑
thyl‑1,3‑dioxolane‑4,5‑dicarboxylate (2h)
Yield: 78 %. White crystalline solid m.p 145–146 °C.
25
−1
25
D
[
α] = 61.14° (c = 24 mg/2 ml CH Cl ). (IR υ cm ):
Yield: 69 %. Brown Oil. [α] = 61.15° (c = 24 mg/2 ml
D
2
2
−
CH Cl ). (IR υ cm ): 2983 (CH), 1748 (COOPh), 1724
2 2
(COOCH ), 1581 (Ar), 1321 (C–O–C), 765 (C–Cl). H
3
1
2
980 (CH), 1748 (COOPh), 1736 (COOCH ), 1580 (Ar),
3
1
1
1
326 (C–O–C), 559 (C–Br). H NMR (400 MHz, CDCl ): δ
3
1
3

J IRAN CHEM SOC
NMR (400 MHz, CDCl ): δ (ppm): 7.48 (s, 1H, Ar–H),
(COOPh), 170.1 (COOCH ), 148.7 (Ar–C–OR), 136.8,
3
3
7
1
.13 (d, J = 8.1 Hz, 1H, Ar–H), 6.93 (d, J = 8.1 Hz,
130.5, 120.3 (Ar–C), 75.1 (CH), 74.1 (CH), 53.7 (OCH3),
20.7 (Ar–CH ). Anal. Calc. For C H O : C, 56.69; H,
5.55; O, 37.76 FoundC, 56.64; H, 5.51; O, 37.73.
H, Ar–H), 5.12 (d, 1H, J = 5.0 Hz, CH), 5.02 (d, 1H,
3
12 14
6
J = 5.0 Hz, CH), 3.86 (s, 3H, O-CH ), 1.56 (s, 6H, CH ).
3
3
1
3
C NMR (100 MHz, CDCl ): δ (ppm): 170.6 (COOPh),
3
1
69.4 (COOCH ), 145.7 (Ar–C–OR), 132.8, 130.5, 128.9,
(2R,3R)‑1‑(3‑Bromophenyl)‑4‑methyl‑2,3‑dihydroxy‑
3
1
27.4, 124.7 (Ar–C), 114.7 (qt, C), 75.8 (CH), 74.9
succinate (3c)
(
CH), 53.8 (OCH ), 26.3 (CH ), 25.5 (CH ). HRMS-ESI
3 3 3
+
25
D
for C H Cl O Na: [M+Na] calcd: 371.0065, found:
Yield: 81 %. Colorless Oil. [α] = 51.25° (c = 24 mg/2 ml
1
4
14
2
6
−
CH Cl ). (IR υ cm ): 3538 (OH), 2985 (CH), 1748
2 2
1
3
71.0069. Anal. Calc. For C H Cl O : C, 48.16; H, 4.04;
1
4
14
2
6
Cl, 20.31; O, 27.49 Found C, 48.13; H, 4.06; Cl, 20.35; O,
7.47.
(COOPh), 1724 (COOCH ), 1569 (Ar), 1321 (C–O–C),
3
2
550 (C–Br).
1
H NMR (300 MHz, CDCl ): δ (ppm): 7.41 (s, 1H,
3
General procedure for the synthesis of compounds
3a–3h)
Ar–H), 7.37–7.31 (m, 3H, Ar–H) 5.06 (d, 1H, J = 4.9 Hz,
(
CH), 4.96 (d, 1H, J = 4.9 Hz, CH), 3.86 (s, 3H, OCH ),
3
1
3
3
.27 (bs, 2H, OH). C NMR (75 MHz, CDCl ): δ (ppm):
3
In a round bottom flask (100 ml), solution of monoaryl
171.5 (COOPh), 170.3 (COOCH ), 148.8 (Ar–C–OR),
3
ester (2a–2h) (1 eq) in DCM was stirred at 0 °C. BF .Et O
132.7, 130.4, 127.6, 126.2 (Ar–C), 75.4 (CH), 73.9 (CH),
52.6 (O–CH ). Anal. Calc. For C H BrO : C, 41.40; H,
3
2
(2 eq) was added drop wise under nitrogen atmosphere.
3
11 11
6
The reaction mixture was then allowed to warm to room
temperature and stirred overnight. After the completion
as indicated by thin layer chromatography (TLC), solvent
was evaporated under reduced pressure. The crude was dis-
solved in ethyl acetate (30 ml), and then washed with water
and brine (30 ml × 3). The organic layer was dried over
anhydrous magnesium sulfate. The crude was further puri-
fied by column chromatography using methanol: chloro-
form (2:8) as eluent.
3.47; Br, 25.04; O, 30.08 Found C, 41.42; H, 3.49; Br,
25.01; O, 30.10.
(2R,3R)‑1‑(3‑Chloro‑4‑methylphenyl)‑4‑methyl‑2,3‑di‑
hydroxysuccinate (3d)
2
5
Yield: 77 %. Yellow Oil. [α] = 67.25° (c = 24 mg/2 ml
D
−1
CH Cl ). (IR υ cm ): 3548 (OH), 2982 (CH), 1745
2
2
(COOPh), 1733 (COOCH ), 1567 (Ar), 1323 (C–O–C),
3
7
66 (C–Cl).
1
(2R,3R)‑1‑Methyl‑4‑phenyl‑2,3‑dihydroxysuccinate (3a)
H NMR (300 MHz, CDCl ): δ (ppm): 7.33 (s, 1H,
3
Ar–H), 7.12 (d, J = 8.4 Hz, 2H Ar–H), 5.11 (d, 1H,
2
D
5
Yield: 86 %. White solid m.p 75–77 °C. [α] = 73.51°
J = 5.5 Hz, CH), 4.92 (d, 1H, J = 5.5 Hz, CH), 3.87 (s,
−
1
13
(
(
(
(
c = 24 mg/2 ml CH Cl ). (IR υ cm ): 3508 (OH), 2965
3H, OCH ), 3.30 (bs, 2H, OH), 2.35 (s, 3H, Ar–CH ).
C
2
2
3
3
CH), 1749 (COOPh), 1733 (COOCH ), 1589 (Ar), 1314
NMR (75 MHz, CDCl ): δ (ppm): 170.5 (COOPh), 169.8
3
3
1
C–O–C). H NMR (300 MHz, CDCl ): δ (ppm): 7.45-7.15
(COOCH ), 147.4 (Ar–C–OR), 134.9, 134.5, 131.4, 120.7,
3
3
m, 5H, Ar–H), 4.84 (d, 1H, J = 5.5 Hz, CH), 4.80 (d, 1H,
117.3 (Ar–C), 74.7 (CH), 73.7 (CH), 53.6 (O–CH ), 19.8
3
J = 5.5 Hz, CH), 3.91 (s, 3H, OCH ), 3.25 (bs, 2H, OH).
(Ar-CH ). Anal. Calc. For C H ClO : C, 49.93; H, 4.54;
3
3
12 13
6
1
3
C NMR (75 MHz, CDCl ): δ (ppm): 171.3 (COOPh),
Cl, 12.28; O, 33.25 Found C, 49.91; H, 4.51; Cl, 12.25; O,
33.27.
3
1
70.5 (COOCH ), 150.7 (Ar–C–OR), 129.9, 126.3, 121.7
3
(
Ar–C), 74.5 (CH), 73.5 (CH), 53.9 (OCH ). Anal. Calc.
3
For C H O : C, 55.00; H, 5.04; O, 39.96 Found C, 55.03;
(2R,3R)‑1‑(3‑Bromo‑4‑methylphenyl)‑4‑methyl‑2,3‑di‑
1
1
12
6
H, 5.07; O, 39.94.
hydroxysuccinate (3e)
2
D
5
(
2R,3R)‑1‑Methyl‑4‑p‑tolyl‑2,3‑dihydroxysuccinate (3b)
Yield: 72 %. White solid. m.p = 176-177 °C.[α] = 68.15°
−1
(
c = 24 mg/2 ml CH Cl ). (IR υ cm ): 3541 (OH), 2980
2
2
2
5
Yield: 78 %. White solid m.p 112-114 °C. [α] = 70.41°
(CH), 1747 (COOPh), 1731 (COOCH ), 1568 (Ar), 1320
D
3
−
1
1
(
(
(
c = 24 mg/2 ml CH Cl ). (IR υ cm ): 3528 (OH), 2975
(C–O–C), 566 (C–Br). H NMR (300 MHz, CDCl ): δ
2
2
3
CH), 1743 (COOPh), 1731 (COOCH ), 1579 (Ar), 1311
(ppm): 7.57 (s, 1H, Ar–H), 7.13 (d, J = 8.4 Hz, 2H Ar–H),
3
1
C–O–C). H NMR (300 MHz, CDCl ): δ (ppm): 7.43 (d,
5.13 (d, 1H, J = 5.4 Hz, CH),4.99 (d, 1H, J = 5.4 Hz,
3
J = 8.9 Hz, 2H, Ar–H), 7.06 (d, J = 8.8 Hz, 2H, Ar–H),
.82 (d, 1H, J = 5.4 Hz, CH), 4.79 (d, 1H, J = 5.4 Hz,
CH), 3.92 (s, 3H, OCH ), 3.28 (bs, 2H, OH), 2.37 (s, 3H,
CH), 3.86 (s, 3H, OCH ), 3.29 (bs, 2H, OH), 2.39 (s, 3H,
3
1
3
4
Ar–CH3). C NMR (75 MHz, CDCl ): δ (ppm): 170.3
(COOPh), 169.9 (COOCH ), 149.7 (Ar–C–OR), 137.5,
133.1, 128.0, 124.9, 120.9 (Ar–C), 75.0 (CH), 74.6 (CH),
3
3
3
1
3
Ar–CH3). C NMR (75 MHz, CDCl ): δ (ppm): 171.6
3
1
3

J IRAN CHEM SOC
5
2.3 (OCH ), 22.6 (Ar–CH ). Anal. Calc. For C H BrO :
O
OH
O
OH
H
3
3
12 13
6
C, 43.26; H, 3.93; Br, 23.99; O, 28.82 Found C, 43.25; H,
.95; Br, 23.97; O, 28.84.
*
*
*
*
H
OH
HO
3
HO
H
H
OH
(2R,3R)‑1‑Methyl‑4‑m‑tolyl‑2,3‑dihydroxysuccinate (3f)
O
OH
O
OH
2
5
Yield: 79 %. Colorless oil. [α] = 74.51° (c = 24 mg/2 ml
D
−
1
Fig. 1 l-(+)-tartaric acid d-(−)-tartaric acid
CH Cl ). (IR υ cm ): 3531 (OH), 2960 (CH), 1750
2
2
(
COOPh), 1732 (COOCH ), 1569 (Ar), 1310 (C–O–C).
3
1
H NMR (300 MHz, CDCl ): δ (ppm): 7.32 (s, 1H, Ar–H),
3
7
.12-6.99 (m, 3H Ar–H), 4.83 (dd, J = 6.9, 2.4 Hz, 1H,
Results and discussion
CH), 4.80 (dd, J = 6.9, 2.4 Hz, 1H, CH), 3.91 (s, 3H,
OCH ), 3.40 (d, J = 6.9 Hz, 1H, OH), 3.35 (d, J = 7.2 Hz,
Synthesis of monoaryl esters (1a–1h)
3
1
3
1
H, OH), 2.38 (s, 3H, Ar–CH ). C NMR (75 MHz,
3
CDCl ): δ (ppm): 171.3 (COOPh), 170.2 (COOCH ), 150.9
For the designing and synthesis of monoaryl esters, we
have started research work with selection of an inexpensive
and commercially available starting material l-(+)-tartaric
acid which has two chiral centers (Fig. 1).
3
3
(Ar–C–OR), 139.5, 129.1, 127.8, 121.2, 118.5 (Ar–C),
7
4.6 (CH), 73.3 (CH), 53.8 (O–CH ), 21.7 (Ar–CH ). Anal.
3
3
Calc. For C H O : C, 56.69; H, 5.55; O, 37.76 Found C,
1
2
14
6
5
6.66; H, 5.57; O, 37.73.
In contrast to the availability of dialkyl tartrates, which
are readily synthesized by Fischer esterification of tartaric
acid or by transesterification of a tartrate with the use of
excess alcohols, di or monoaryl tartrates remained until
now virtually unknown. We carried out many synthesis
procedures for acid activation toward the synthesis of aryl
esters; however, they did not afford any aryl esters on reac-
tion with tartaric acid. Cysewski et al. [31] have reported
the synthesis of diaryl esters from dimethyl-2,3-O-ben-
zylidene-l-tartrate and addressed the difficulties for direct
esterification of tartaric acid with aryl alcohols.
Herein we report a facile synthesis of monoaryl esters
of l-tartaric acid. The monoester of l-tartaric acid is not
commercially available; however, we synthesized up to
30 g scale in good yield [32]. In the synthetic sequence, the
first step was to protect the diacid functionality as dimethyl
ester and diol as 1,3-dioxolane. Different protecting groups
can be used to avoid unwanted side reactions of hydroxyl
groups. We chose 2-methoxypropene as a protecting group
to furnish 1,3-dioxolane. 1,3-Dioxolanes are widely used in
natural product syntheses as protecting groups for ketones,
aldehydes, and 1,2-diols. It is stable in basic condition. It is
also an important intermediate and end product in different
pharmaceutical, fragrance, and polymer industries [33–36].
Kucuk et al. [36] have reported the synthesis of 1,3-diox-
olane derivatives of l- and d-tartaric acid using 2,2-dimeth-
oxy propane.
(2R,3R)‑1‑(2‑Bromophenyl)‑4‑methyl‑2,3‑dihydroxy‑
succinate (3g)
2
D
5
Yield: 76 %. Yellow oil. [α] = 57.15° (c = 24 mg/2 ml
−
1
CH Cl ). (IR υ cm ): 3521 (OH), 2980 (CH), 1748
2
2
(COOPh), 1725 (COOCH ), 1579 (Ar), 1313 (C–O–C),
3
5
59 (C–Br).
1
H NMR (300 MHz, CDCl ): δ (ppm): 7.65–7.19 (m,
3
Ar–H), 5.16 (d, J = 5.4 Hz, 1H, CH),5.13 (d, J = 5.4 Hz,
1
3
1
H, CH), 3.87 (s, 3H, OCH ), 3.25 (bs, 2H, OH).
C
3
NMR (75 MHz, CDCl ): δ (ppm): 170.5 (COOPh), 168.9
3
(COOCH ), 145.8 (Ar–C–OR), 136.9, 134.1, 129.0, 127.7
3
(Ar–C), 76.3 (CH), 75.2 (CH), 52.5 (O–CH ). Anal. Calc.
3
For C H BrO : C, 41.40; H, 3.47; Br, 25.04; O, 30.08
Found C, 41.43; H, 3.49; Br, 25.01; O, 30.10.
1
1
11
6
(2R,3R)‑1‑(2,4‑Dichlorophenyl)‑4‑methyl‑2,3‑dihydrox‑
ysuccinate (3h)
Yield: 70 %. White crystalline solid. m.p = 103–105 °C.
25
−1
[
α] = 66.15° (c = 24 mg/2 ml CH Cl ). (IR υ cm ):
D
2
2
3
531 (OH), 2970 (CH), 1744 (COOPh), 1725 (COOCH ),
569 (Ar), 1311 (C–O–C), 768 (C–Cl). H NMR
3
1
1
(300 MHz, CDCl ): δ (ppm): 7.51 (s, 1H, Ar–H), 7.19 (d,
3
J = 7.7 Hz, 1H, Ar–H), 6.89 (d, J = 7.7 Hz, 1H Ar–H),
.14 (d, J = 5.5 Hz, 1H, CH), 5.08 (d, J = 5.5 Hz, 1H,
CH), 3.88 (s, 3H, OCH ), 3.29 (bs, 2H, OH). C NMR
5
First, the dimethyl-l-tartrate was prepared from l-tar-
taric acid and methanol [37] (Scheme 1). 1,3-Dioxolane
dimethyl-l-tartrate (1) was prepared from dimethyl-l-tar-
trate following the literature procedure [32–38]. The initial
yield was poor and once the reaction conditions were opti-
mized, the yield was improved to 89 %. The product was
purified through column chromatography.
1
3
3
(75 MHz, CDCl ): δ (ppm): 171.4 (CO–O–Ph), 170.7
3
(CO–O–CH ), 146.9 (Ar–C–OR), 134.6, 133.4, 129.3,
3
1
28.2, 126.8 (Ar–C), 73.2 (CH), 53.6 (O–CH ). Anal. Calc.
3
For C H Cl O : C, 42.74; H, 3.26; Cl, 22.94; O, 31.06
Found C, 42.76; H, 3.28; Cl, 22.99; O, 31.08.
1
1
10
2
6
1
3

J IRAN CHEM SOC
O
OH
O
OH
OH
O
MeOH, H
2-Methoxypropene
O
O
O
O
O
CSA, DMF, N , rt
O
reflux, 2 hr
2
O
HO
HO
overnight
OH
O
O
L-tartaric acid
1
Dimethyl-L-tartrate
O
O
OH
NaOH (1 eq)
O
MeOH, rt, 2 hr
O
O
2
Scheme 1 Synthesis of 1,3-dioxolane dimethyl-l-tartrate (1) and monoester (2)
Our next step was to partially hydrolyze compound (1)
using sodium hydroxide (1 eq.) in methanol [32, 39]. Initial
attempts to prepare the desired monoester resulted in low
yield. When the reaction time was increased from one to two
hours and when the drop wise addition of sodium hydroxide
solution was increased, the yield was further improved. The
in 4.87–4.72 ppm with coupling constant of 5.4 Hz in each.
The two methyl groups of 1,3-dioxolane appeared as sin-
glets at 1.49 and 1.48 ppm with integration of three protons
for each singlet. In C NMR spectrum, peak at 173.8 ppm
was assigned to CO (acid) and 169.7 to CO (ester).
Methine carbons appeared at 76.8 and 75.7 ppm, respec-
tively. EI-MS described in the experimental protocol also
confirmed the synthesis of monoester, the molecular ion
(m/z) appeared in the mass spectrum was in agreement with
the molecular weight of the compound.
1
3
resultant salt was acidified with aqueous KHSO (1 M). To
4
remove some of the unreacted starting material and diacid,
the product was purified with column chromatography to
get the monoester (2) as colorless oil, in 79 % yield.
After the monoester in hand, it was coupled with differ-
ent substituted phenols using EDC as dehydrating agent to
afford compounds (2a–2h) in 69–87 % yields (Scheme 2).
All the compounds were purified and characterized by
spectral analysis.
The compounds (1) and (2) were characterized using
IR, H NMR, C NMR, and EI‑MS
1
13
The IR absorption spectrum of the compound (1) showed
−
1
characteristic bands at 2928 and 1738 cm . These absorp-
IR spectral data of the monoaryl esters (2a–2h) exhib-
ited characteristic CO stretching bands in the range of
1
tions were attributed to C-H and CO, respectively. In H
−1
1
NMR spectrum, a singlet at 4.45 ppm with integration of
two protons was attributed to CH, singlet at 3.82 ppm with
integration of six protons was assigned to two methoxy
groups, and another singlet at 1.57 ppm with integration of
six protons was assigned to two methyl groups of 1,3-diox-
1756–1743 and C–O–C in 1324–1311 cm . H NMR
spectral data show doublets in para-substituted phenol
(2b), while ortho- and meta-substituted phenols (2g, 2f)
1
3
showed multiplets and singlets, respectively. In C NMR,
peaks in 170.7–169.3 and 168.2–167.7 ppm were assigned
to CO (aryl) and CO (methyl), respectively; the aromatic
carbons appeared in the range of 150.8–121.8 ppm. Ele-
mental analysis of these compounds, described in the
experimental protocol further supported the structures of
all the compounds. Formation of monoaryl esters was also
confirmed by high-resolution mass analysis. Observed
1
3
olane. In C NMR spectrum, peak at 170.3 ppm was
assigned to CO of ester group. Another peak at 113.5 ppm
was attributed to quaternary carbon. The chiral methine
carbon appeared at 76.4 ppm. The two carbon of the meth-
oxy groups appeared at 52.3 ppm. The methyl carbon of
1
,3-dioxolane appeared at 25.7 ppm, respectively.
+
The IR spectral data of compound (2) showed character-
HRMS-ESI of the [M+Na] and calculated values were in
−
1
istic stretching bands at 3467, 2928, 1730, and 1708 cm .
These absorptions were assigned to OH, C-H, CO (ester),
agreement with each other. Finally, the synthesis of mono-
aryl ester derivatives was supported by the crystal structure
of (4R,5R)-4-(3-Bromo-4-methylphenyl)-5-methyl-2,2-di-
methyl-1,3-dioxolane-4,5-dicarboxylate (2e) by X-ray
crystallography (Fig. 2).
1
and CO (acid), respectively. In H NMR, a broad singlet at
9
.32 ppm with integration of one proton was attributed to
OH group. The two methine protons appeared as doublets
1
3

J IRAN CHEM SOC
O
O
OH
O
O
O
O
EDC, DCM, N2
+
HO
O
O
O
DMAP, rt, 4-12 hr
R
R
O
O
2
2a-2h
S. No.
Code
R
R
f
values*
0.62
0.74
0.69
0.68
0.57
0.66
0.75
0.64
Yield (%)
1
2
3
4
5
6
7
8
2a
2b
2c
2d
2e
2f
H
78
83
85
87
78
80
74
69
4-Methyl
3-Bromo
3-Chloro-4-methyl
3-Bromo-4-methyl
3-Methyl
2g
2h
2-Bromo
2,4-Di-chloro
*
Solvent system: Ethyl acetate:Hexane (3:7)
Scheme 2 Synthesis of monoaryl esters (2a–2h)
Fig. 2 Crystal structure
of (4R,5R)-4-(3-bromo-
4
2
4
-methylphenyl)-5-methyl-
,2-dimethyl-1,3-dioxolane-
,5-dicarboxylate (2e). Thermal
ellipsoids are shown at the 50 %
probability level
On the basis of IR, H NMR, 13C NMR, HRMS-ESI,
and single-crystal X-ray analysis, it was confirmed that the
monoaryl ester derivatives were synthesized successfully.
1
production of industrial pharmaceuticals, dyes and agro-
chemicals [40]. The reaction involves acylium ion interme-
diates that are generated from the ester by interaction with
an acid catalyst. More specifically, the Fries rearrangement
of phenyl acetate (PAc) yields ortho- and para-hydroxyace-
tophenones (o-HAP and p-HAP) which are very valuable
precursors in the pharmaceutical industry, being this reac-
tion the first step of the Hoechst Celanese manufacturing
process of paracetamol [41]. Classical Fries rearrangement
Attempted Fries rearrangement of monoaryl esters
(2a–2h)
The selective Fries rearrangement of esters of aro-
matic alcohols serves as a valuable synthesis step in the
1
3

J IRAN CHEM SOC
O
O
O
O OH
R
O
O
O
BF .Et O, DCM
3
2
O
O
O
or
O
or AlCl , N2
3
R
O
O
O
OH
0
°C-rt, overnight
O
O
R
2a-2h
Expected rearranged products
O
O
OH
OH
BF .Et O, DCM
3
2
O
no rearrangement
or AlCl3
R
O
0
°C-rt, overnight
reflux, 2 hr
Actual products 3a-3h
Scheme 3 Attempted Fries rearrangement of monoaryl esters (2a–2h)
is generally catalyzed by acids like hydrofluoric acid (HF)
the experimental protocol further supported the structures
of all the compounds.
[
42], the most frequently used AlCl [43], BF [44], TiCl ,
3 3 4
or SnCl [45].
4
In our ongoing effort to generate new C–C bond and
chiral substrates, monoaryl esters (2a–2h) were pro-
cessed following the literature procedures for the Fries
rearrangement.
Conclusions
Monoaryl esters (2a–2h) were synthesized from monoester
of l-tartaric acid and processed further in Fries rearrange-
ment to get chiral ketones. The rearrangement was tried
under various conditions by using different Lewis acids.
The actual products obtained were only the deprotected
analog and no rearrangements occur. The structure of com-
pound 2e in the series was also confirmed by X-ray crys-
tallography. The synthesized monoaryl esters have large
optical rotations and will be served as lead compounds for
further research in organic chemistry.
The Fries rearrangement of compound (2a) was first
tried using BF ·Et O in DCM (Scheme 2).
3
2
After overnight stirring and purification of new product
as indicated by TLC, no rearrangement occurs; instead we
1
got the deprotected product which was confirmed by H
NMR.
The reaction was then tried with AlCl . After purifica-
3
1
tion and characterization with H NMR, we got compound
2
a with free diol. The reactions were then tried for rest of
the compounds (2b–2h) using different Lewis acids but all
the products obtained were only the deprotected analog and
no rearrangement occurs as confirmed by spectral analysis.
The deprotected compounds (3a–3h) obtained were also
tried using the same reaction conditions and with additional
reflux for 2h but no reactions occur (Scheme 3).
Acknowledgments This work was financially supported by Higher
Education Commission (HEC), Pakistan under International Research
Support Initiative Program (IRSIP) and “National Research Program
for Universities.”
All the deprotected compounds were purified and char-
acterized by spectral analysis.
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